1. Field of Invention
The invention relates to a module for the production of concrete elements, particularly of concrete semi-finished products or of concrete surfaces, and a displacement body for use in such a module according.
The invention concerns in particular a module for the production of concrete elements, in particular of concrete semi-finished products or of relatively “thin” concrete surfaces, with a plurality of displacement bodies which are able to be inserted, arranged adjacent to each other in a longitudinal direction, in which the plurality of displacement bodies arranged adjacent to each other is arranged respectively undetachably in a latticework of bars.
2. Description of Related Art
Such modules are known from the prior art; they are used principally in the production of relatively thick concrete surfaces.
Such a module is known for example from WO 2005/080704-A1. In this module, the latticework has a base side running in the longitudinal direction and two partial sides adjoining the base side and arranged obliquely with respect to the base side, but likewise running in the longitudinal direction. The latticework which is used has a channel-like form with a wide channel base and a narrow channel opening. The displacement bodies arranged in the latticework are plastic balls.
A disadvantage of the type of construction according to WO 2005/080704-A1 consists in that with greater manufacturing tolerances of the upper lattice bar spacings, the plastic balls partially protrude to a different extent upwards out from the latticework, which has the result that the required covering values (layer thickness of the concrete over the balls) are possibly not able to be kept. In addition, there is a risk of damage for the displacement bodies.
A further such module is known from DE 202006002540 U1. In this module, also, the latticework has a channel-like form, but with a narrow channel base and a wide channel opening. The displacement bodies arranged in the latticework are likewise plastic balls. In this type of construction of the latticework, the risk of damage for the displacement bodies is considerably reduced and the covering values can be kept more reliably.
However, a disadvantage both in WO 2005/080704-A1 and also in DE 202006002540 U1 is that for thin concrete surfaces the structure of the module can not be simply reduced in size as desired. This is because the manufacturing costs of the modules are greatly increased by the increasingly required quantity of balls per unit of area. As the wire diameter for the latticework generally also can not be reduced for reasons of stability, a considerable increase in material can also occur here even for this reason. In addition the risk exists that the ball spacings become too small with respect to the current grain size of the concrete, which then results in that concrete-free “nests” can occur in the concrete surface which is to be finished, because the concrete can not distribute itself well. Furthermore, the compacting of the concrete by means of so-called vibrating needles proves to be difficult owing to the unfavourable accessibility. The simple reduction in size of all components therefore comes up against certain limits very quickly.
In the older prior art, there are various solutions with non-spherical and frequently rectangular displacement bodies, which from their static generic form are to be regarded as rib surfaces. However, these displacement bodies are generally not embedded in a latticework and therefore are also not protected against floating; i.e. additional steps must be taken for this purpose. In addition, in fact in the case of rectangular displacement members the force distribution lines within the stressed concrete surface lie so unfavourably that large intermediate zones are produced, in which the stress concentrations (on loading of the concrete surface) become so high that the risk of local failure exists in the concrete mass surrounding the displacement bodies. This disadvantage is eliminated for example by the additional introduction of reinforcing steel in these intermediate zones, which, however, leads to an additional aggravating condition in the construction sequence and to an increased requirement for material. In addition, the size of the area of the lower plane of these displacement bodies can lead to the guaranteeing of the underflowing of the concrete only being able to be ensured with specific concrete compositions and with an additional processing expenditure.
The problem therefore exists that in the case of “thin” concrete surfaces, such as for instance short-span surfaces in house construction or in skyscrapers, neither the module concept according to WO 2005/080704-A1 or DE 202006002540 U1 nor the previously usual concept with rectangular or flat displacement bodies can be readily undertaken. In the former case (i.e. with spherical displacement bodies), the mere reduction in size leads to the stated problems with regard to cost and handling, whereas in the latter case (i.e. with, for example, rectangular displacement bodies), an unnecessarily large extent of structural strength of the concrete surface is provided.
It is therefore an object of the invention to indicate an improved module for the production of concrete elements, in particular of concrete semi-finished products or of “thin” in-situ concrete surfaces and a displacement body for use in such a module, by which the disadvantages known from the prior art are circumvented.